It is difficult to study diet in relation to cancer in the USA because of the uniformity of dietary practices in this country. Seventh-day Adventists (SDA's) are a conservative religious group who do not smoke or drink by church proscription, and about 50 per cent of them do not use meat, coffee, tea and hot spices. SDA's are very health oriented, and many of them use whole grains and other unrefined foods abundantly in their diet. Previous studies have demonstrated that cancer mortality in SDA's is 1/3 that of the general population for most cancer sites. This data is based on mortality data which only measures risk of cancer death. It is very likely that SDA's are actually at low risk of developing cancer, and if so, it is important to determine what characteristics of the life style pattern among SDA'S account for this low risk. Considerable evidence exists in the literature suggesting that many of the components of the SDA life style other than nonsmoking may be related to low cancer risk (low residue diet and colon cancer, food-born carcinogenic viruses or chemicals, excessive fat or protein and cancer, conservative sex life and cervical cancer etc.). The proposed prospective study will collect detailed information on the demographic and medical characteristics and life style components of 78,000 SDA's living in California. They will be followed for 5 years to ascertain all new cancer cases by reviewing hospital records for all hospitalizations occuring during the study period. A study among SDA's who have low cancer mortality and a unique life style is likely to be productive of new clues useful in cancer prevention. Since there is great variablity among SDA's in degree and time of adherence to unique habits (i.e. vegetarianism, unrefined, high residue diet, lack of coffee, etc.), it will be possible to relate these habits to cancer risk in subgroups of the population that are homogeneous in other respects. Elucidation of previously undiscovered factors protective against cancer could have considerable implications in cancer prevention and in increasing knowledge of mechanisms of carcinogenesis.